Applied Mechanics and Materials Vol. 889

Abstract: Porous NiTi alloys were successfully synthesized by two different processes, including self-propagating high-temperature synthesis (SHS), and a combined process of decomposition – sintering. A systematic comparison of micro-structures and mechanical properties of these alloys was investigated. The results showed that the SHS process was better than decomposition – sintering process. By controlling the processing parameters of SHS, the received porous NiTi alloys showed that the porosity and pore were larger, and ratio of opened-pore reached up to 80%. The porous NiTi alloys fabricated by SHS process also exhibited good properties, such as a high compressive strength (up to 250MPa), and elastic modulus in range of 6.1 – 7.0GPa. The porous NiTi alloys synthesized by decomposition – sintering process have lower porosity (26-43%), lower compressive strength (< 110MPa), lower elastic modulus (< 1.2GPa) but the strain could be reached to 10%.

Abstract: The volatile organic compounds (VOCs) contribute to serious air pollution problems in Viet Nam. Many studies have investigated in air quality monitoring and treatment, in order to determine the average concentrations of Benzene, Toluene, Ethylbenzene and Xylene (BTEX). Carbon nanotubes (CNTs) have been widely used as adsorbent in environmental treatment, especially for VOCs. This paper aims to determine the adsorption capacity of multiwalled carbon nanotubes for removal of BTEX from air samples. In preliminary study, the effects of various parameters during adsorption experiments were monitored such as flow rate, temperature and BTEX concentrations in air samples. The equipment for BTEX removal was developed by our research team consisting of filter columns, air sample bags, adsorption cartridge. The air samples containing BTEX were conducted directly through a cartridge packed with adsorbent. The adsorption experiments were carried out under various operating conditions such as temperature (30 - 40°C), gas concentration (0,57 - 4,77 mg/L) and the gas flow rate (10 - 90 mL/min). In addition, isotherm studies of CNTs for BTEX removal were achieved by using Langmuir and Freundlich models. The results showed that the experimental parameters were optimized at a flow rate of 30 mL/min and an ambient temperature at 30°C. The adsorption capacity of CNTs increased proportionally with BTEX concentrations. The specific affinity of CNTs for BTEX from air samples was in order of X > E > T > B. The experimental isotherm data were well-fit with the Langmuir model for Benzene and Xylene removal, and the Freundlich model for Toluene and Ethylbenzene adsorption. The CNTs presented highly potential application for BTEX adsorption thanks to their microporous structure and high surface area.

Abstract: The extensive range of fillers used nowadays indicated the major significance of filler in the plastic industry. Although their original purpose was to lower the cost of the molding compounds; prime importance is now attached to selective modification of the properties of a specific plastic. In this study, the examples of LDPE/EVA blends, were put into 0, 3, 6, 9, 12 and 15 wt.% of EVA. The tensile strength, bending strength and impact strength of samples were determined according to ASTM D638, ISO 178 and ISO 179. Results showed that when increasing ratio of EVA in LDPE/ EVA blends, tensile strength decreased from 10.9 MPa to 8.6 MPa. Bending strength decreased linearly from 9.63 MPa to 5.46 MPa. Charpy impact strength decreased from 47.5 kJ/m² to 6.3 kJ/m². On the contrary, elongation in 100% LDPE is 78.3%; with the appearance of EVA, elongation of the LDPE/ EVA blends increased upto 109.1%. In addition, SEM micrographs indicated that, it was more crystal-clear when the EVA content is less; in the highest EVA content with 15%, it can be seen that the specimen after pressing is slightly opaque and darker than the orthers. From that showed the addition of EVA to the polymer leads the tensile strength, bending strength were not affect much, impact strength decreased but elongation experienced an increase.

Abstract: Nowadays, the original source of mineral fuel for engines was depleting increasingly while combustion products make the environment to be polluted, CO₂ emission which caused many greenhouse gases; this also makes crude oil prices fluctuate and rise. They tend to use biogas as a fuel for internal combustion engines which have been interested in the powerful countries. Supply of biogas from the waste of farms, flour production, fish processing, landfills, etc., with hundreds or thousands of cube meter of biomass daily leads demand on high-power generators using biogas in order to make good use of produced gas. This article introduces a technology solution for fuel engines using purely large-capacity biogas and operating under compression type fire. Accordingly, the tubular biogas Venturi mixer with electronic controller has been used to supply the mixture of fuel to engine. The CDI-DC ignition circuit provides a high voltage of 28kV for forced combustion of the mixture. Experimental results show that the mixer operates stably, well controlled and allows adjusting the ratio of air/fuel, as well as easily changing its speed when it is used as a hybrid engine for the generator. Some results of performance evaluation of biogas mixer will be presented in this article.

Abstract: Vegetable oil is used directly as a fuel, in either modified or unmodified equipment, it is referred to as straight vegetable oil (SVO). SVOs have some advantages in comparison with fossil fuel oils such as: renewability, local availability, lower sulfur content, etc. avoiding the environmental effects caused by sulfuric acid, lower aromatic content and high biodegradability. However, SVOs are also attached to several disadvantages such as: high viscosity, low heating value, high fatty contents, influencing on injection process and causing engine coking if misused. In order to prevent such negative effects of diesel engine fuelled by SVO, one of potential solutions is using blends of SVO with diesel oil (DO). In such case, the reasonable ratio of SVO and diesel oil plays a very important role for normal running condition, but also seems to be challenge to identify. The article shows results of a study on defining the ratio for marine diesel application. It is firstly based on the assessment on the heat release processes inside the diesel engine cylinder upon a specific simulation with different blends of SVO and diesel oil. In comparison with the particular requirements for fuel of marine engines, the preferable percentage of vegetable oil in the fuel mixture is pointed out. And finally, the experiments with fuel system of a typical marine diesel engine, HANSHIN 6LU32, installed at the lab of Vietnam Maritime University in terms of checking real engine’s operation and reducing harmful emissions.

Abstract: This study presents the possibility of producing syngas from the industrial scale continuous downdraft coffee husk gasifier. Experimental results show that, the ratio of main combustible gases obtained in syngas is as follows: CO » 29.07 %, H₂ » 11.97 %, CH₄ » 2.16 %. Moreover, the effect of temperature on the ratio of components of syngas was determined. Through the experimental optimization process, optimal technological parameters so that the quality of syngas obtained is best achieved, was determined, specifically: moisture content (10.52 %); wind flow (56.75 m³/h); fuel consumption rate (100.35 kg/h).

Abstract: Equilibrium moisture content (EMC) of Ganoderma Lucidum was determined experimentally at three different experimental temperature (30, 40 and 50°C) and relative humidity ranged from 11.1 to 93.58% using a gravimetric technique. The experimental data of equilibrium moisture content obtained was fitted to four mathematical models (Modified Henderson, Modified Chung ˗ Pfost, Modified Oswin and Modified Haley). A non-linear least square regression analysis was used to evaluate the model constants based on the parameters as: standard error of estimate (SEE), the residual sum of squares (RSS), the quadratic regression coefficient (R²). The result showed that the modified Chung ˗ Pfost model best fitted the experimental data.

Abstract: The domestic anthracite is the most important fuel for Vietnamese thermal power plants. Due to high carbon percentage and low volatile matter it is difficult to ignite and to burn out the domestic anthracite. The rest carbon in ash is very high, in some cases approximately 40 %. To solve this problem some methods have been tested. In this research a mixture of anthracite and coal gas is considered. The purpose of the research is to describe a combustion behavior in a boiler, namely temperature, carbon and volatile matter distributions using CFD. The mixture consists of 4.3 % coal gas and 95.7% anthracite in mass. The boiler is divided into two combustion zones, the main zone 1 and the zone 2, to extend combustion area and through it to improve burning conditions for anthracite particles and to reduce NOx formation. All the anthracite mass and 1/3 coal gas volume are delivered into the zone 1, the rest of coal gas is into the zone 2. The CFD simulation is used for the zone 1. The simulation findings show that anthracite particles are ignited earlier, the mixture combustion develops in a larger space with higher temperatures, the carbon burning rate is remarkably improved due to coal gas. That means the domestic anthracite can be used better in boilers if some coal gas, 4 or 5 %, is mixed and the obtained ash can have lower unburned carbon, below 10%, and be more friendly for the environment.

Abstract: This paper presents the production of enviromental concrete using fine aggregate and fly ash to reduce bad influences on environment. The excessive exploition of traditional sand in Mekong Delta rivers has recently caused serious landslides sweeping away a large area and making. Therefore, using alternative materials - fine aggregate to replace river sand - is very important and urgent. In addition, fly ash is one of waste products in coal-fired power plants, and, the consumption of fly ash helps decreasing landfill costs and increasing sustainable development. The compression strength of environmental concrete is obtained from 20-40 MPa using cube-shaped specimens with various compositions. The productive prices between environmental and traditional concrete are comparatively discussed

Abstract: The tensile and bending properties of composite materials with geopolymer matrix reinforced by layers of basalt plain weave fabric were investigated experimentally. We present the results of the quasi-static tensile tests and the quasi-static and cyclic three-point bending tests. The composite panels were made by hand laying with subsequent vacuuming. The plates were stayed in a compression press and left in a compressed state for a month. After 5 months the samples were made from the plates and subjected to tests. The material behaves as linear almost to the failure, which occurred at tensions of about 100 MPa. The elastic modulus is between 6000 and 7000 MPa.